Deception In Aerial Warfare Part 1- Stealth

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The Lockheed F117 Nighthawk is covered using this paint.

“All warfare is based on deception.” This famous line was quoted by Sun Tzu, a Chinese military strategist, who perished thousands of years ago. Till date, he is treated as one of the finest brains behind developing the science of warfare through his book “The Art of War”. For Sun Tzu, deception, mobility and formations outweighed the effects of strength in numbers and firepower. His teachings and preachings pertaining to warfare are used to carve out warfare strategies and SOPs even today. 

Deception is basically painting a wrong picture in the minds of the enemy leaders, so that they cannot anticipate your next move and “the element of surprise” is conserved. 

For example, if you’ve watched the very famous movie, “Lakshya” starring Hrithik Roshan as Lt. Shergill, and Amitabh Bachchan as Col. Damle. The objective of Col. Damle’s unit in the movie was a peak, which apparently had cover-less ground on three sides, and on one side, it had a straight 90 degree inclined feature. A company from Col. Damle’s unit opens fire on the enemy sitting at the top of the peak from the flat grounds, making them believe that the Indian Army will attack from that very direction, but meanwhile, a platoon from the unit climbs up the 90 degree slope to attack the enemy from the rear in an unanticipated move. They made the enemy believe what was not true, and thus, made their next move a complete surprise. This is deception. 

Let us now talk about deception in aerial warfare. Deception in air combat is facilitated by Aircraft stealth, which is a combined effect of reduced IR signature, RCA, reduced acoustic signature and electronic warfare capabilities. Those aircraft which are not easily visible to the enemy radars, are called stealth aircrafts. 

  1. IR signature or infrared signature – IR signature is the parameter which defines the inability of an aircraft to hide itself from heat seeking cameras (Infrared cameras). Heat seeking cameras have thermal sensors in them which capture electromagnetic  radiations. Most of these radiations are in the Infrared region, and the higher the radiation (heat from the engine), stronger the impressions will be. Man ported air defence systems like the Igla-S have super cooled nitrogen and an IR homing device, which read the heat differential between the liquid nitrogen and aircraft exhausts. Therefore, even the most suppressed heat signatures are susceptible to such AD systems. Aircraft engines and its exhausts are super heated and can reach temperatures as high as 1300 degree celsius. Therefore, they leave a pretty good impression on thermal cameras. In order to alleviate IR Signatures, the exhaust plumes are kept non circular, which reduces the exhaust cross sectional area, and cool ambient air mixed with the hot air. In some aircrafts, coolant fluids like jet fuel are circulated inside the exhaust pipes, to mitigate the heating effect.
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An aircraft as viewed from an infrared camera. Red- High temperatures, blue- cool temperatures. ( Source: researchgate.net)

2. Acoustic Signature – Acoustic Signature is a parameter which is used to define sound and vibratory emissions from an aircraft. An aircraft while traveling through the air, produces cacophonous vibrations, which are heard and observed by enemy observation posts. Although it is not a very precise parameter to detect aircrafts (since sounds can be produced by nearly all vibratory bodies in the vicinity of the OPs), it plays quite a significant role in aerial operations. One can understand its importance by taking in account, the choice of Sikorsky UH60 Black Hawk helicopter in “Op Neptune Spear- killing of Bin Laden”. The Black Hawk was preferred over Chinook to transport the US Navy Seals since it has a low radar and acoustic signature. It produces considerably lesser sound than its other counterparts, and does its work very silently and stealthily. The noise from a helicopter is mainly because of its rotors. Therefore, much of the sound reduction can be done by attaching spoilers and a covering at the rotors. Apart from this, not much has been developed in Acoustic signature reduction technology.

 

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Tail rotor covering
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Stealth Helicopter. Notice its weird shape and covered tail rotor.

3. RCS or Radar Cross Sectional Area – It is a parameter that defines how much an aircraft is susceptible to a radar. Larger the RCS, easier will it be to detect the aircraft. The RCS depends upon various factors including the airframe (size and shape of aircraft), material by which the aircraft is made etc. The transmitter of a radar emits radio waves, which propagate through the atmosphere and are reflected back by objects flying in the skies (aircrafts/UAVs). The reflected waves are identified by the receiver of the radar set, and then, by some simple mathematical calculations, the whereabouts of the aircraft are presented to the radar operators. 

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We have multiple methods to hide an aircraft from the radars, the main ones being –

  • Purpose shaping – The curvature of an aircraft are replaced by sharp shapes in this method. To simply understand this, we can take the example of a circle. If we drop a straight line (analogous to a radar wave) on a circle (analogous to a reflecting surface of an aircraft) in its radial direction, we’ll find out that the line traces back its original track. This line or the wave, is received again by the radars receiver, and accurate presentation of the aircraft’s position, speed and altitude are provided to the operators. Purpose shaping removes all the curved surfaces, and replaces them with sharp cuts, which reflect radio waves like a plane mirror in other directions.

 

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Working of a Radar.
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How purpose shaping works.
  • How purpose shaping works, Active Cancellation – When two waves, of the same amplitude and frequency, but 180 degree phase difference superimpose with each other, they produce a zero wave (destructive interference).

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Notice in the above picture, that under destructive interference, the two waves are almost similar, but are completely opposite. This results in both the waves cancelling out each other, and a zero wave is produced. In active cancellation stealth, the radar waves are read by the aircraft, and a similar wave with the same frequency and amplitude but with opposite orient (180 degree phase shift) is emitted from the aircraft’s transmitter. Thus the wave coming from the ground radar, and the wave produced by the aircraft undergo superposition resulting into a destructive interference pattern (zero wave).

  • Radiation Absorbent Material – Radiation Absorbent Material or RAM is a type of material used to produce the airframe of an aircraft. The aircrafts produced using RAMs are less prone to radar systems. However, it does not make the aircraft completely invisible to the radar, which was the case in aircrafts incorporating Active cancellation. The most commonly used RAM is iron ball paint. The iron ball paint comprises of tiny molecular spheres coated with ferrite. When radar waves (basically a type of electromagnetic wave) fall on these molecules, these molecules perform oscillatory motions dissipating the radar wave’s energy as heat energy.

So far, we have discussed the first and the most important part of aerial deception- Stealth. We have understood what stealth is, how is it produced and why is it produced. 

In the next part, we will see, how different manoeuvres and formations can deceive an enemy.

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Dheeraj Choudhary is a Physics Undergrad from the University of Jodhpur, he served in the Air Wing of the National Cadet Corps for two and a half years and is currently in possession of a 'B' Certificate with Alpha Grading. His love for aviation, military and strategic affairs started in his early teens when he would look at the Mig-21, Mig-27, and Su-30's roaring in the skies of his hometown Jodhpur. He's been reading and writing about aviation since then and is looking forward to flying an aircraft someday. His blogs on aviation are in simple and easy English for promoting better understanding for all aviation enthusiasts